Milk composition having reduced mineral content

ABSTRACT

A sterilized milk composition is based upon the natural constituents of milk and has reduced phosphorous, sodium, potassium and citrate contents. The composition is derived, in particular, from skimmed milk and has a non-fat dry matter solids content which includes, by weight based upon the weight of the non-fat solids, from 33% and 36% protein, 48% to 58% lactose and 3% to 5% minerals, and the minerals include a calcium content in an amount of from 75% to 100% of that of the skimmed milk, a phosphorous content in an amount of from 50% to 75% of that of the skimmed milk, a sodium content in an amount of from 5% to 20% of that of the skimmed milk, a potassium content in an amount of from 5% to 20% of that of the skimmed milk and a citrate content in an amount of from 10% to 30% of that of the skimmed milk.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of application Ser. No.08/162,863, filed Dec. 6, 1993, now U.S. Pat. No. 5,503,865.

BACKGROUND OF THE INVENTION

The present invention relates to a dairy composition.

Evaporated milk is characterised by a relatively high concentration ofminerals present in its soluble phase, in particular ions not linked tothe casein micelle, such as sodium and potassium cations, and anionssuch as chloride and certain phosphates and citrates. Up until now,attempts have been made, in particular, to stabilise evaporated milkduring the technological process of concentration by evaporation byadding stabilising salts thereto, such as citrates and phosphates, toprotect the proteins during the preservation heat-treatment and to avoidthe thickening and separation of the phases during storage. These salts,by increasing still further the proportion of minerals not linked to themicelle, have the effect of impairing the organoleptic qualities of themilk, particularly its taste. In addition, the heat-treatment assiststhe stabilisation of the evaporated milk but affects its taste andwhiteness.

A process is known, for example, from French Patent ApplicationPublication No. 2 644 983, for preparing a liquid composition which usesmicrofiltration or ultrafiltration of skimmed milk in order to produce,based on a residue with a reduced lactose content, a composition inwhich the lactose is replaced by a non-milk sugar, for example a fruitand starch sugar. The overall composition of this product is no longerthe same as that of milk.

SUMMARY OF THE INVENTION

The object of the invention is to provide a dairy compositionapproximating milk, based on natural components of milk havingorganoleptic and dietetic characteristics which are appreciably improvedcompared with evaporated milk.

The composition according to the invention is characterised by the factthat it contains, by weight of non-fat solids, 33 to 36% protein, 48 to58% lactose and 3 to 5% minerals, and by the fact that, amongst theminerals, the calcium content is 75 to 100% of that of milk, thephosphorus content is 50 to 75% of that of milk, the sodium andpotassium contents are each 5 to 20% of that of milk and the citratecontent is 10 to 30% of that of milk. The composition thus is based uponnatural constituents of milk and has a reduced phosphorus sodium,potassium and citrate content as compared with the milk from which it isderived.

DETAILED DESCRIPTION OF THE INVENTION

In the above definition of the invention, and in the remainder of thedescription, the percentages and contents stated result from analysis ofthe substances by the usual analysis methods applied to milk.

Within the scope of the invention, the milk may come from any mammalianmilk-bearing female, for example cattle, goats or sheep.

The composition according to the invention may be in a concentratedliquid form, for example with 20-30% by weight of non-fat dry matter, ordiluted to a greater or lesser extent by reconstituting with water or anaqueous liquid. It may contain up to 15% by weight of fats. It may alsobe in the form of a powder after drying, for example by spray drying,intended to be reconstituted in a liquid form by the addition of wateror an aqueous liquid.

It has been found that the composition according to the invention hasremarkable organoleptic properties characterised by increased smoothnessand a clean fresh taste compared with milk and especially compared withevaporated milk, and improved whiteness compared with evaporated milk.In addition, it has, in a concentrated form, remarkable stability instorage, without precipitation of salts, for example calcium citrate.

The invention also provides a process for preparing the abovecomposition, characterised in that skimmed milk is concentrated byultrafiltration or microfiltration to a factor of 3 to 6 times by volumeand in that, in the retentate, a quantity of lactose is dissolvedcorresponding, by weight, to approximately the quantity of dry matter inthe retentate.

Preferably, the original skimmed milk is pasteurised.

According to a first embodiment of the process, the above liquid mixtureis dried, for example by spray drying or freeze drying.

In a second embodiment of the process, the liquid concentrate is mixedwith previously sterilised cream, the mixture is homogenised and is thenhermetically packaged in containers, and the containers are sterilised,for example in an autoclave.

In a preferred embodiment of the process according to the invention, theretentate and an aqueous lactose solution are sterilised separately, theretentate and lactose solution are mixed aseptically, previouslysterilised milk fat is added thereto, and the mixture is homogenised andaseptically packaged in containers.

Where applicable, the mixture is post-sterilised under moderateconditions of heat before being packaged aseptically.

As a variant of the operations following homogenisation, the homogenisedmixture may be packaged in containers which are closed hermetically, andwhich are then sterilised under moderate conditions of heat, for examplein an autoclave.

In the process of the invention, it is preferred to concentratepreviously pasteurised skimmed milk by using microfiltration on mineralmembranes preferably having a porosity of approximately 0.1 to 0.2microns. Ultra-filtration can also be used for this operation, but thereis a preference for microfiltration, which affords a better permeationrate and a higher concentration than those obtained by ultrafiltration(for example, up to six times by volume). Unlike ultrafiltration, whichallows the retention of whey proteins, microfiltration largelyeliminates them. In a particularly preferred version of this process,the microfiltration is continued with a washing or diafiltrationoperation, at constant volume, for example with a volume ofdemineralised water approximately three times that of the retentate. Theaim of this operation is an additional reduction in the minerals notbound to the casein micelle, in particular the sodium and potassiumcations. After the diafiltration, concentration can preferably becarried out once again, for example until a dry matter content ofapproximately 20% by weight is obtained.

It may be desirable to keep some of the whey proteins in the retentatewhilst using microfiltration for the purpose of increasing theproportion of dry matter of protein origin. To do this, the originalskimmed milk is heat treated under relatively severe conditions, at atemperature of 90° C. to 140° C. and for a period of 20 s to 10 min, thehighest temperature corresponding to the shortest period and vice versa.This treatment brings about the aggregation of the whey proteins and theretention of the aggregates.

The permeate of the microfiltration or ultrafiltration constitutes auseful raw material which can be demineralised, for example by ionexchange and/or electrodialysis in order to be used, for example, inbaby products.

When it results from microfiltration, this permeate also has theadvantage of having a low microbe content.

As mentioned previously, the preferred process is the one in which theretentate and lactose are sterilised separately from each other. To dothis, the retentate is preferably sterilised by ultra high temperature(UHT), at 120°-150° C. and preferably 130°-140° C. Sterilisation takesplace by maintaining this temperature for 15 to 60 s. The lactose isdissolved in hot demineralised water at the highest possibleconcentration, for example at saturation. Sterilisation of the lactoseis used at a temperature and for a duration comparable to thoseapplicable to the retentate, which causes any lactose remaining insuspension to be redissolved. This lactose solution, once sterilised, ismaintained at a temperature of 50° C. or more and mixed with theretentate, preferably at 50°-60° C., so as to prevent recrystallisationof the lactose before and during the mixing. Preferably, the pH(measured at 50°-60° C.) is adjusted if necessary to a value >6.8, forexample by the addition of an aqueous solution of calcium hydroxide.

After addition of the previously sterilised milk fat, in the form ofbutter oil or cream, the subsequent homogenisation preferably takesplace at 50°-55° C. in two stages, for example at a pressure of 10-30MPa for the first stage and 2.5-5 MPa for the second.

Whatever the variant of the post-sterilisation stage, for example by UHTor in an autoclave, the conditions used correspond to moderate heattreatment, preferably, in the case of UHT treatment at 135°-145° C. for3-5 s, for example at approximately 140° C. for 3 s, or 120°-125° C. for1-3 min, and for example at approximately 121° C. for 2 min in the caseof treatment in an autoclave. It is possible to use mild treatmentconditions since the microorganisms have been completely inactivatedduring the relatively severe sterilisation treatment of the retentateand lactose. In this way the effect of Maillard's reaction is minimised.

The dairy composition obtained constitutes a base, characterised byexcellent qualities of smoothness and taste, for products such asconcentrates, desserts and culinary or dietetic products, for examplewith a low sodium content.

The following examples illustrate the invention. In these examples, theparts and percentages are by weight, unless otherwise indicated.

EXAMPLES Example 1

250 kg of skimmed milk is pasteurised at 72° C. for 14 s and is thensubjected to tangential microfiltration on a TECHSEP S 151 unit fittedwith CARBOSEP M 14 membranes with a total surface area of 3.2 m². Theoperation is carried out at 50° C. until the milk/retentate volume ratiois 6. At this stage the dry matter content of the retentate is 24% andthe permeation flow is 1/3 of its initial value. Its dry matter contentis then adjusted to 20% and lactose is added thereto at 2 kg of lactoseper 10 kg of retentate. The mixture is agitated at 50° C. until thelactose is completely dissolved and is then dried by freeze drying.

The powder obtained has the composition indicated in Table 1 below incomparison with that of skimmed milk, expressed as a percentage of thetotal solid matter (including the residual moisture).

                  TABLE 1                                                         ______________________________________                                                       % of total solid matter                                                                   Skimmed                                            Constituent      Example 1 milk                                               ______________________________________                                        Protein (N × 6.38)                                                                       35        35                                                 Fat              1         1                                                  Lactose          57.6      51.9                                               Ash              4.2       7.8                                                Citrate          0.5       1.7                                                Ash, including                                                                Calcium          1.1       1.3                                                Phosphorus       0.7       1.0                                                Potassium        0.3       1.6                                                Sodium           0.1       0.6                                                ______________________________________                                    

After reconstitution with demineralised water so as to obtain 48 g oflactose/kg, the liquid composition obtained from the powder was assessedorganoleptically in comparison with pasteurised skimmed milk with thesame lactose content and with a skimmed milk powder dried by spraydrying low temperature and reconstituted with water, with the samelactose content. The panel of tasters found that the compositionaccording to the invention had a smoothness and taste which were muchmore pleasant than the pasteurised or recombined skimmed milk.

Example 2

A composition containing 23% of non-fat solids and 10% fat is producedby homogenising appropriate quantities of the retentate/lactose mixtureof Example 1 and cream, sterilised by UHT, having a 35% fat content, andthen sterilising the homogenised product in an autoclave.

Tasting the composition obtained showed that it was smoother than atraditional evaporated milk with the same proportions of non-fat solidsand fats, even more marked than in the case of a non-concentrated milk.

Example 3

250 l of skimmed milk is pasteurised at 72° C. for 14 s and isconcentrated by microfiltration as in Example 1 until a milk/retentatevolume ratio of 3 is obtained. At this stage, diafiltration of theretentate against demineralised water is carried out until 250 l ofpermeate is produced. The introduction of demineralised water is thenstopped and the retentate is then concentrated to a final volume of 40l. After the addition of lactose in proportions of retentate solids tolactose solids of 0.442 to 0.558 until the lactose is completelydissolved, the mixture is dried by spray drying.

The powder obtained has the composition shown in Table 2 below.

                  TABLE 2                                                         ______________________________________                                                       % of total solid matter                                                                   Skimmed                                            Constituent      Example 3 milk                                               ______________________________________                                        Protein (N × 6.38)                                                                       35        35                                                 Fat              1         1                                                  Lactose          57.5      51.9                                               Ash              3.5       7.8                                                Citrate          0.3       1.7                                                Ash, including                                                                Calcium          1.1       1.3                                                Phosphorus       0.7       1.0                                                Potassium        0.2       1.6                                                Sodium           0.04      0.6                                                ______________________________________                                    

After reconstitution with water as in Example 1, and after the additionof cream as in Example 2, respectively, the liquid composition obtainedfrom the powder had a smoothness and taste which were much more pleasantthan the pasteurised or recombined skimmed milk with the same non-fatsolid content, and the full cream milk with the same non-fat solid andfat contents, respectively.

Example 4

250 l of skimmed milk is heat treated at 135° C. for 21 s in UHTequipment. This treatment brings about an almost complete denaturationof the whey proteins. Microfiltration with diafiltration of the milkthus treated is then carried out as in Example 3, and then the retentateis concentrated to 1/6 of the initial volume of milk. Analysis of thetotal proteins contained in the retentate shows that 6.11 kg of proteinsis obtained, whilst 5.65 kg of proteins is obtained by the process ofExample 3. It can be concluded from this that the retention of the wheyproteins was appreciably improved by the heat treatment of the milk. Thelactose content is then adjusted and the mixture is then dried asindicated in Example 3.

The powder obtained has the composition indicated in Table 3 below.

                  TABLE 3                                                         ______________________________________                                                       % of total solid matter                                                                   Skimmed                                            Constituent      Example 4 milk                                               ______________________________________                                        Protein (N × 6.38)                                                                       35        35                                                 Fat              1         1                                                  Lactose          56.4      51.9                                               Ash              3.4       7.8                                                Citrate          0.3       1.7                                                Ash, including                                                                Calcium          1.0       1.3                                                Phosphorus       0.7       1.0                                                Potassium        0.2       1.7                                                Sodium           0.04      0.6                                                ______________________________________                                    

After reconstitution with water as in Example 1, and with the additionof cream as in Example 2, respectively, the liquid composition obtainedfrom the powder had the same qualities of smoothness and taste as thecompositions of Examples 1, 2 and 3. This means that the presence ofdenaturated whey proteins in the retentate in no way effects theorganoleptic qualities of the compositions, the protein yield beingmoreover increased.

Example 5

Skimmed milk is pasteurised at 72° C. for 15 s, and is then concentratedby microfiltration on a mineral membrane with a nominal pore dimensionof 0.2 microns, until a volume of retentate is obtained equal to 1/6 ofthe volume of milk put in. Diafiltration of the retentate is thencarried out at constant volume with 3× its volume of demineralisedwater, and it is then concentrated to 20% of dry matter. The retentateis then sterilised at 135° C. for 20 s by UHT and is placed in a steriletank.

Separately, lactose is dissolved in demineralised water, at 80° C. andat a concentration of 60%, that is to say the maximum possible. Thelactose is not completely dissolved, but its complete dissolution isobtained when it is subsequently treated by UHT at 135° C. for 30 s.After sterilisation, the lactose is stored in a sterile tank.

The retentate and lactose solution are then mixed aseptically inproportions corresponding, for 87% of proteins out of the total solidsof the retentate, to 40% of retentate solids for 60% of lactose solids.This mixing is carried out under agitation at 50°-60° C. Cream with a35% fat content, previously sterilised by UHT, is then added to thismixture in an appropriate quantity to obtain 23% non-fat solids for 10%fat, at 50°-55° C. The pH is then adjusted to 6.8-6.9 (determined at50°-60° C.) by the addition of an aqueous dispersion of calciumhydroxide, if it does not already have this value.

The mixture is then homogenised at 50°-55° C. in two stages, the firstat 15 MPa and the second at 3 MPa, and it is then post-sterilised at140° C. for 5 s and is packed aseptically in containers.

The dairy composition has a lightness of 84.55 (L value measured byspectrophotometry on MACBETH 2000) and 5.83% of blocked lysine. Bycomparison, a commercially available evaporated milk has a lightness of75.49 L and 36.98% blocked lysine.

Example 6

The process is carried out as in Example 5 except for thepost-sterilisation, which is carried out in an autoclave at 120° C. for2 min after packing the product in hermetically sealed containers.

The dairy composition has a lightness of 80.77 L and 13.84% blockedlysine.

We claim:
 1. A sterilized milk composition derived from a skimmed milkand comprising non-fat dry matter solids which comprise, by weight basedupon the weight of the non-fat solids, from 33% and 36% protein whichcomprises casein micelle, 48% to 58% lactose and 3% to 5% minerals andwherein the minerals include a calcium content in an amount of from 75%to 100% of that of the skimmed milk, a phosphorous content in an amountof from 50% to 75% of that of the skimmed milk, a sodium content in anamount of from 5% to 20% of that of the skimmed milk and a potassiumcontent in an amount of from 5% to 20% of that of the skimmed milk andwherein citrate is in an amount of from 10% to 30% of the skimmed milkcitrate content.
 2. A milk composition according to claim 1 wherein thenon-fat dry matter solids are in an amount of from 20% to 30% by weightbased upon the weight of the composition.
 3. A milk compositionaccording to claim 1 further comprising a fat.
 4. A milk compositionaccording to claim 2 further comprising a fat.
 5. A milk compositionaccording to claim 3 wherein the fat is in an amount of up to 15% byweight based upon the weight of the composition.
 6. A milk compositionaccording to claim 4 wherein the fat is in an amount of up to 15% byweight based upon the weight of the composition.
 7. A milk compositionaccording to claim 1 wherein the composition has a pH of at least 6.8.8. A milk composition according to claim 1 wherein the composition has apH of from 6.8 to 6.9.
 9. A milk composition according to claim 1wherein the protein further comprises denatured whey protein.
 10. A milkcomposition according to claim 1 wherein the composition is amicrofiltered retentate.
 11. A milk composition according to claim 1wherein the composition is an ultrafiltered retentate.